Method of manufacturing a piston for a hydraulic motor having radial pistons

Abstract

A method for manufacturing radial pistons for a hydraulic motor by machining cylindrical transverse holes at regular intervals in a bar, and, in order to form two adjacent pistons, cutting up the bar on a transverse cutting-up plane passing through one of said holes so that a first portion of said hole forms a cradle-shaped recess in the base of the first one of the two adjacent pistons and so that another portion of said hole forms a cradle-shaped recess in the top of the second one of the two adjacent pistons.

The invention claimed is: 
     
       1. A method of manufacturing pistons for a hydraulic motor having radial pistons, each piston having a base, a top and a cradle-shaped recess, the method comprising the steps of:
 providing a cylindrical bar having a longitudinal axis, 
 machining cylindrical transverse through holes spaced apart uniformly in the bar, and 
 in order to form two adjacent pistons, cutting up the bar on a transverse cutting-up plane passing through one of said holes, so that a first portion of said hole forms a cradle-shaped recess having substantially the shape of a fraction of a cylinder in the base of the first one of the two adjacent pistons and so that another portion of said hole forms a cradle-shaped recess having substantially the shape of a fraction of a cylinder in a top of the second one of the two adjacent pistons. 
 
     
     
       2. A method according to  claim 1 , wherein the transverse cutting-up plane is offset relative to a transverse plane of symmetry of the hole through which said cutting-up plane passes so as to form the cradle-shaped recess in the base of the first one of the two adjacent pistons to be smaller than the cradle-shaped recess formed in the top of the second one of the two adjacent pistons. 
     
     
       3. A method according to  claim 1 , wherein additional machining operations, comprising at least one of rectification, treatment, de-burring, coating, lining, turning and milling are performed on the bar before the cutting step.